I'm sure there's linkage adjustment, generally if you can get into the gears eventually, means you need to adjust something. I would get the bentley manual and whatever resources you can for you car to do it correctly. A little common sense checking things out might help too. I don't know off the top of my head what the adjustment is, but if I was in your position I would hit up the previous suggestions.
is the problem with one or more of the gears??
once you get it in is it crunching
how does the clutch feel??
and there is no adjustment on linkages for bmw manual boxes they are solid linkages from your gear box back so if there is nothing jamming it externaly then it is a problem internaly